Poa annua, also known as annual bluegrass, is a weed that can cause unsightly spots in your lawn during the spring when poa annua seed heads bloom and in the summer when the weed dies.
Treating poa annua can be tricky as seeds can lay dormant for years before growing. That's why a two-step approach to poa annua treatment may be necessary. Both pre-emergents and post-emergents will control poa annua in your yard. Read below to learn more.
Apply a Pre-Emergent Herbicide
As their name suggests, pre-emergent herbicides are applied before weeds emerge. In the case of poa annua, that means applying a pre-emergent herbicide like Dimension 2EW, Hi-Yield Weed and Grass Stopper, Barricade 4FL, or another pre-emergent labeled for poa annua on your lawn before poa annua seeds begin to germinate.
Read the label of any pre-emergent you may consider using to be sure it is compatible with the type of lawn you have. Not all pre-emergents can be used on all grass types.
Apply in the fall before the first frost occurs, before the soil temperature reaches 70 degrees or below. If you live in an area that does not have frost, you would apply before temperatures drop. The timing of your application depends on where you live. Consult our lawn care calendars to determine when to apply your pre-emergent herbicide treatment.
It is advised that you do two fall pre-emergent herbicide treatments, spaced 30 days apart from one another. This will help ensure your entire lawn is treated, reducing the number of spots you might miss with one treatment. It will also increase the amount of time the pre-emergent treatment will last.
You will also need to apply a spring pre-emergent herbicide treatment sometime between late January and early May, before temperatures rise and weeds begin to germinate. Again, consult our seasonal calendars or contact your local extension office for timing advice.
Watch the video below to learn how to apply a pre-emergent herbicide.
Apply a Post-Emergent Herbicide
A post-emergent herbicide treatment can be used to kill any poa annua that grows in the spring and was missed by your pre-emergent herbicide treatment. Post-emergent herbicides work best when used in conjunction with pre-emergent herbicide treatments.
Selecting the post-emergent herbicide treatment depends on the type of grass you have and the area being treated. As poa annua is technically a cool season grass, it is very similar to other cool season grasses, like Kentucky bluegrass or ryegrass. If you have a cool season grass, spot treating (Step 3) may be your best option. Be sure to read the label of your post-emergent herbicide to be sure the product is appropriate for the area of application.
Watch the video below to learn how to apply a post-emergent herbicide to your lawn.
(Optional) Spot Treat Your Yard
If you still have a few poa annua weeds in your lawn after both pre- and post-emergent herbicide treatments, try using a non-selective herbicide that is labeled as a post-emergent, like Roundup Pro Max or Roundup QuickPro, to spot treat the weeds. The non-selective post-emergent herbicide will kill poa annua weeds and the turf where it is sprayed. Be sure to read the label of your non-selective post-emergent herbicide to understand the impact it will have on your lawn.
Keep in mind, poa annua will die and turn brown in the summer when temperatures are consistently 85 degrees Fahrenheit and higher. If you have hot days on the horizon, you may want to wait before applying a spot treatment.
Not sure if you have poa annua in your yard? Read our guide on what poa annua looks like to make a positive identification before you treat. If you have had problems with poa annua in the past, read our guide on how to prevent poa annua from growing to learn how to be proactive in your treatment process. Click the right arrow below to read more.